The present invention relates, in general, to an air conditioning system with low compression load and, more particularly, to an air conditioning system designed to preferably reduce the compression load of its compressor by reducing the temperature of refrigerant flowing into the compressor.
In the prior art, an air conditioning system, designed to perform its heating or cooling function by taking advantage of the phase change of the refrigerant to dissipate or absorb heat to or from air of a target room using the phase change of the refrigerant, has been proposed and widely used. In a heating or cooling operation, the air conditioning system repeatedly carries out a refrigerating cycle where refrigerant is sequentially subjected to a compression process, a condensation process, an expansion process, and an evaporation process prior to being returned to the compression process.
The conventional air conditioning systems have been classified into three types: a cooling system designed to cool a target room, a heating system designed to heat a target room, and a heating/cooling system designed to heat or cool a target room in accordance with its operational mode selected by a user.
In the conventional heating systems or the conventional cooling systems, refrigerant flows through a fixed passage. However, the heating/cooling system is designed such that refrigerant flows through a heating mode passage or a cooling mode passage in accordance with its operational mode selected by a user.
Each of the conventional heating systems, cooling systems and heating/cooling systems comprises an indoor unit, an outdoor unit, a compressor, and an expansion unit. The indoor unit is installed within a room, while the outdoor unit is installed outside the room. The compressor adiabatically compresses low temperature, low pressure gas refrigerant to discharge high temperature, high pressure gas refrigerant. The expansion unit adiabatically expands high temperature, high pressure gas refrigerant to discharge low temperature, low pressure liquid refrigerant. The indoor unit, outdoor unit, compressor, and expansion unit are connected together by a refrigerant pipeline to allow refrigerant to flow through them during an operation of the air conditioning system. A plurality of sensors are installed at predetermined positions of the air conditioning system to sense the temperature and pressure of the refrigerant. The operation of the air conditioning system is controlled by a controller, which controls power supply for the electrically operable elements, such as the compressor, the sensors, etc., in addition to controlling the operation of the elements in response to signals output from the sensors. Particularly, the heating/cooling system has a plurality of control valves, which are used for changing the refrigerant flowing passage in accordance with a selected operational mode of the system.
The conventional cooling system or the conventional heating/cooling system is operated as follows when it is desired to cool a target room using the system.
At the indoor unit, low temperature, low pressure liquid refrigerant absorbs heat from air inside the target room prior to being discharged to the compressor. At the compressor, the low temperature, low pressure gas refrigerant from the indoor unit is compressed to become high temperature, high pressure gas refrigerant prior to being discharged to the outdoor unit. At the outdoor unit, the high temperature, high pressure gas refrigerant from the compressor dissipates heat to atmospheric air, thus being condensed to become high temperature, high pressure liquid refrigerant prior to being discharged to the expansion unit. The expansion unit adiabatically expands the high temperature, high pressure liquid refrigerant from the outdoor unit to discharge low temperature, low pressure liquid refrigerant to the indoor unit. The system thus finishes one operation cycle.
The conventional heating system or the conventional heating/cooling system is operated as follows when it is desired to heat a target room using the system.
At the indoor unit, high temperature, high pressure gas refrigerant dissipates heat to air inside the target room, thus being condensed to become high temperature, high pressure liquid refrigerant prior to being discharged to the expansion unit. The expansion unit adiabatically expands the high temperature, high pressure liquid refrigerant from the indoor unit to discharge low temperature, low pressure liquid refrigerant to the outdoor unit. At the outdoor unit, the low temperature, low pressure liquid refrigerant from the expansion unit absorbs heat from atmospheric air, thus being evaporated to become low temperature, low pressure gas refrigerant prior to being discharged to the compressor. At the compressor, the low temperature, low pressure gas refrigerant from the outdoor unit is compressed to become high temperature, high pressure gas refrigerant prior to being discharged to the indoor unit. The system thus finishes one operation cycle.
In such conventional air conditioning systems, it is typical to control the temperature of inlet refrigerant of the compressor such that the temperature is increased to slightly exceed the saturation point of the refrigerant, where the refrigerant includes both a gas phase portion and a liquid phase portion. When the temperature of the inlet refrigerant of the compressor is increased as described above, the inlet refrigerant is converted entirely to gas refrigerant. When refrigerant including a liquid phase portion flows into the compressor, the refrigerant may undesirably deteriorate the refrigerant compressing capability of the compressor, in addition to damaging or breaking the parts of the compressor.
When the temperature of inlet refrigerant of the compressor is increased excessively to exceed the saturation point of the refrigerant, the inlet refrigerant may thermally damage the parts of the compressor to cause a thermal deterioration of the parts and undesirably shorten the expected life span of the compressor, in addition to remarkably reducing the compression efficiency of the compressor.
However, such conventional air conditioning systems do not include any means for appropriately controlling the conditions of inlet refrigerant of their compressors, and so the inlet refrigerant of the compressor undesirably has a temperature excessively exceeding the saturation point of the refrigerant, where the refrigerant includes both a gas phase portion and a liquid phase portion.
The compressor""s inlet refrigerant having such an excessively increased temperature thermally damages the parts of the compressor to cause a thermal deterioration of the parts and undesirably shorten the expected life span of the compressor, and forces the owner of the air conditioning system to waste time and pay money for repairing the air conditioning system.
The inlet refrigerant having such an excessively increased temperature also undesirably causes the outlet refrigerant from the compressor to have excessively high temperature or excessively low pressure.
When the outlet refrigerant from the compressor has an excessively high temperature, it is necessary for the refrigerant to dissipate an excessively large quantity of heat to surrounding air during a condensation process. When the outlet refrigerant from the compressor has an excessively low pressure, it is almost impossible to desirably condense the refrigerant during the condensation process since the temperature of the refrigerant is too low. Either of the two cases undesirably reduces the heat and/or cooling effect of the air conditioning system.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide an air conditioning system, which is designed to prevent the temperature of the inlet refrigerant of its compressor from being increased excessively to exceed the saturation point of the refrigerant with both a gas phase portion and a liquid phase portion of the refrigerant, and which thus preferably reduces the compression load of the compressor.
Another object of the present invention is to provide an air conditioning system, which reduces the compression load of its compressor, thus being free from a reduction in its heating and/or cooling efficiency.
A further object of the present invention is to provide an air conditioning system, which reduces the compression load of its compressor, thus being free from a thermal deterioration of the compressor""s parts or a reduction in the expected life span of the compressor.
In order to accomplish the above objects, the primary embodiment of the present invention provides an air conditioning system designed such that the condensed refrigerant from the indoor unit or the outdoor unit passes through a heat exchanging, sub-evaporating unit prior to flowing into the expansion unit, with the refrigerant from the sub-evaporating unit partially flowing into a sub-expansion unit to be adiabatically expanded to become low temperature, low pressure bypassed refrigerant prior to flowing into the compressor through the sub-evaporating unit.
The second embodiment of the present invention provides an air conditioning system designed such that the condensed refrigerant from the indoor unit or the outdoor unit passes through a heat exchanging, sub-evaporating unit prior to flowing into the expansion unit, with the refrigerant from the sub-evaporating unit partially flowing into a sub-expansion unit to be adiabatically expanded to become low temperature, low pressure bypassed refrigerant, and both the bypassed refrigerant flowing from the sub-expansion unit and the refrigerant flowing from the outdoor unit or the indoor unit commonly passing through the sub-evaporating unit prior to flowing into the compressor.
The third embodiment of the present invention provides an air conditioning system designed such that the condensed refrigerant from the indoor unit or the outdoor unit passes through a heat exchanging, sub-evaporating unit prior to flowing into the expansion unit, with the refrigerant from the sub-evaporating unit partially flowing into a sub-expansion unit to be adiabatically expanded to become low temperature, low pressure bypassed refrigerant, and both the bypassed refrigerant flowing from the sub-expansion unit and passing through the sub-evaporating unit and the refrigerant flowing from the outdoor unit or the indoor unit and passing through the expansion unit commonly flowing into the compressor.
The fourth embodiment of the present invention provides an air conditioning system designed such that the condensed refrigerant from the indoor unit or the outdoor unit passes through a heat exchanging, sub-evaporating unit prior to flowing into the expansion unit, with the refrigerant from the sub-evaporating unit partially flowing into a sub-expansion unit to be adiabatically expanded to become low temperature, low pressure bypassed refrigerant, and both the bypassed refrigerant flowing from the sub-expansion unit and the refrigerant flowing from the outdoor unit or the indoor unit and passing through the expansion unit commonly passing through the sub-evaporating unit prior to flowing into the compressor.